Marama beans, Tyosema esculentum, is classified in the Leguminosae family and the Caesalpinioideae sub-family. The marama plants grow in semi-desert climates in South Africa and Australia. Marama beans have a high level of trypsin inhibitors (239TUI/mg protein) which is about twice that reported for soybeans.
The antiprotease present in marama beans has recently been isolated and partially characterized. Beans were obtained from Southern Africa and were part of the same lot used in a nutritional study. The hard shells were cracked, the oily kernel removed and the inhibitor extracted essentially as described by Wagner and Rheim, 1967, using an ethanol wash and solubilization in dilute HCl. An ammonium sulfate cut was taken between 40 and 80 percent saturation, dialyzed and freeze dried. This fraction represented approximately 10% of the total protein in the bean. Analysis of this fraction on SDS acrylamide gels revealed a single but rather diffuse band with a molecular weight around 18,000.
The molecular weights of the proteinase inhibitors range between 20,000 to 27,000 at least five different trypsin inhibitors are present as well as two elastase inhibitors.